Preparation of beryllium hydrides

ABSTRACT

Beryllium hydride is prepared by disproportionation of a haloberyllium hydride-Lewis base complex.

United States Patent [191 Murib et al.

PREPARATION OF BERYLLIUM HYDRIDES Inventors: Jawad H. Murib; StuartSchott;

Charles A. Bonecutter, all of Cincinnati, Ohio Appl. No.: 763,968

Related US. Application Data Continuation-impart of Ser. No. 316,532,Oct. 16, 1963, abandoned.

US. Cl. 423/645; 149/109 [4 1 Nov. 4, 1975 [51] Int. Cl C01b 6/00 [58]Field of Search 23/204; 423/645 [56] References Cited UNITED STATESPATENTS 3,483,219 12/1969 Shepherd 149/109 X Primary Examinerl ,eland A.Sebastian Attorney, Agent, or FirmAl1e:n A. Meyer, Jr.

[57] ABSTRACT Beryllium hydride is prepared by disproportionation of ahaloberyllium hydride-Lewis base complex.

7 Claims, No Drawings PREPARATION OF BERYLLIUM HYDRIDES This is acontinuation-in-part of application Ser. No. 316,532, filed Oct. 16,1963, and now abandoned.

Beryllium hydride is of considerable importance in powder metallurgy andin space and military applications as a high energy fuel component. Itsinsolubility in inert solvents, however, greatly hinders its beingpurified to the level required for its use. Previous attempts to obtainhigh purity beryllium hydride have not been successful. For example,impurities remained in the beryllium hydride obtained by the pyrolysisof di-tbutyl beryllium (prepared from Grignard reagent) at about 200C.(G. E. Coates and F. Clockling, J. Chem. Soc., 1526 (1954), according tothe equation The removal of the impurities in the beryllium hydrideobtained by the above method is difficult because of the insolubility ofberyllium hydride in inert solvents.

It has now been found that high purity beryllium hydride can be preparedfrom a soluble form of a haloberyllium hydride, that is, from a Lewisbase complex of haloberyllium hydride that has been formed by reacting ahydride of an alkali metal or an alkaline earth metal with a solution ofa beryllium halide in the presence of a Lewis base.

In general a metal hydride or a complexed metal hydride, suspended ordissolved in an inert medium, is added to a stoichiometric equivalent ofa beryllium halide in an inert solvent along with a Lewis base, theamount of the Lewis base being at least equimolar to the amount of theberyllium halide. The resulting mixture is agitated until the formationof insoluble by-product alkali metal halide or alkaline earth metalhalide is essentially complete. The solution of the producthaloberyllium hydride complex is then separated from the insolubleby-product halide by any convenient means.

The solution of the haloberyllium hydride can then be heated withdistillation of the Lewis base, whereupon solid beryllium hydride,substantially free of impurities, is precipitated.

The preparation of haloberyllium hydride from a beryllium halide and analkali metal hydride or an alkaline earth metal hydride is carried out,in accordance with the present invention, in the presence of a Lewisbase at temperatures below 100C. and in a closed system as illustratedby the following equation:

wherein M is an alkali metal or an alkaline earth metal; X is a halogenselected from the group consisting of chlorine, bromine and iodine; Z isa Lewis base; and n ranges between 0.5 and 2.

After completion of the reaction, the soluble haloberyllium hydride canbe readily separated from the insoluble metal species (i.e., by-productMX and residual MH) by filtration thereby obtaining soluble XBel-I:Z,,,free of alkali or alkaline earth metal ions. The product can then bedisproportionated in a second step in the absence of metal ions to givesolid BeH and soluble BeX according to the following equilibriumreaction:

wherein X, Z and n are as defined above in connection with Eq. 1.

The reaction in Eq. 2 can be shifted to the right direction by employingany method that facilitates removal of the Lewis base from the system.For example, distillation of the Lewis base at any temperature betweenabout 25 to 175C. leads to formation of solid beryllium hydride. Vacuumdistillation of the Lewis base from the reaction mixture permitsoperation at low temperatures, for example, between 50 and 100C.However, when the reaction (Eq. 2) is carried out in a closed system,i.e., without distillation of the Lewis base, high temperatures, i.e.above 100C, are required to effect the disproportionation. It ispreferred, however, to operate the disproportionation reaction (Eq. 2)at below 100C. under vacuum in order to minimize incorporation ofinsoluble by-products in the final beryllium product. Thus, in the caseof using diethyl ether as the Lewis base, the undesirable by-productsinclude insoluble species derived from ether cleavage such as XBeOC Hand HBeOC I-l Although these compounds are soluble in aromatichydrocarbons, the occluded impurities could not be removed by extractionwith these solvents. Therefore, it is preferred to employ temperaturesat which cleavage of ether does not occur. In the case where the productXBel-lzOEt is prepared in aromatic hydrocarbons at relatively hightemperatures, e.g. 100C, any by-product of ether cleavage can beseparated by stripping off the aromatic solvent and subsequentdissolution of the product in ether followed by filtration of theinsoluble impurities and finally by distilling off the excess etherthereby obtaining pure haloberyllium hydride-etherate.

The beryllium halide suitable for the practice of this invention can beberyllium chloride, beryllium bro mide, or beryllium iodide. It ispossible to use instead of the halide other salts such as the alkoxides,e.g., beryllium methoxide or beryllium isopropoxide; the mercaptides,e.g., beryllium ethyl mercaptide or beryllium isobutyl mercaptide; andthe like. When these beryllium salts are used it is preferred to usearomatic hydrocarbons as media for the reaction of Equation 1.

The metal hydride can be any simple alkali metal hydride, alkaline earthmetal hydride, or mixture thereof, e.g., Lil-I, NaH,Kl-l, CsH, Mgl-l andCal-l or complex metal hydride having the formula M( HM'R or M(HM'(OR')wherein M is an alkali metal or alkaline earth metal, M is boron oraluminum, R is hydrogen, an alkyl radical having from 1 to about 5carbon atoms or an aryl radical having from 6 to about 9 carbon atoms, Ris an alkyl radical having from 1 to about 5 carbon atoms or an arylradical having from 6 to about 9 carbon atoms, and n is one or two.

The Lewis base is an electron pair donor that does not contain an acidichydrogen and can be selected from groups of dialkyl ethers such asdimethyl ether, diethyl ether, methylethyl ether, dipropyl ether,dibutyl ether, B,B-dichloroethyl ether; diaryl ethers such as diphenylether, tolyl phenyl ether and ditolyl ether; alkyl aryl ethers such asanisole and ethyl phenyl ether; dialkyl sulfides such as dimethylsulfide, diethyl sulfide, n-propyl sulfide, di-n-butyl sulfide and ethylmethyl sulfide; tertiary amines such as trialkylamines (trimethylamine,triethylamine and trin-propylamine), pyridines (2-ethyl pyridine and2-n-propyl pyridine), piperidines (n-methyl piperidine, n-ethylpiperidine and n-propyl beryllium halide reactant and the haloberylliumhydride product and must be chemically inert to both the reactant andthe product. It should also be relatively volatile to permit easyremoval from the product. Suitable media include ,saturated aliphatichydrocarbons and aromatic hydrocarbons, such as kerosene, hexane,nonane, isooctane benzene, toluene, xylene, and mesita ylene; inertchlorinated hydrocarbons, such as chlorobenzene, 2,4-dichlorotoluene,oand p-chlorotoluene,

o-chloroben'zene, p-dichlorobenzene, and o-xylyl chloride; andhalogenated acyclic hydrocarbons, such as trichloroethylene andmethylene dichloride; and the like; and mixtures of these.

It is also possible to have one of the Lewis bases listed above serve aspart or all of the solvent in the haloberyllium hydride formationreaction (Eq. .1), in which case an amount of Lewis base in excess ofthat required to complex the beryllium halide is employed.

In carrying out the disproportionation reaction it is preferred that thereaction medium have a higher boiling point than any Lewis base presentin order to be able to selectively remove the Lewis base bydistillatron.

Any solvent and Lewis base used in the process of the present inventionmust be free from moisture and peroxides. The beryllium halides shouldbe anhydrous in order to avoid hydrolysis of the active hydride whichwould result in poor yields and conversions as well as low reactionrates.

The preferred molar ratio of metal hydride (M-H bonds) to the berylliumcontent in the reaction mixture is 1:1. At higher ratios of metalhydride, the intermediate HBeX tends to react with the excess metalhydride to prematurely form beryllium hydride (Bel-l which would bedifficult to separate from the insoluble metal halide being formed.Lower ratios of metal hydride lead to incomplete conversion of theberyllium halide and make the subsequent disproportionation reactionmore difficult.

The amount of Lewis base used is at least equimolar to the amount ofberyllium halide. Preferably, 2 or more moles of Lewis base per mole ofberyllium halide are used.

The solvent should be used in a quantity sufficient to maintain insolution both the reactant beryllium halide- Lewis base complex and theproduct haloberyllium hydride-Lewis base complex.

The reaction in which the haloberyllium compound is found is generallycarried out at a temperature at which its disproportionation is minimal,that is, in the range of about to 100C. and preferably in the range ofabout 25 to 85C. The accompanying pressure need only be sufficient tomaintain the solvent in liquid phase, and is preferably, but notnecessarily, that which permits the removal of the Lewis base bydistillation.

By the process of this invention beryllium hydride of high purity can beobtained, the solubility of haloberyllium hydrides in certain organicsolvents offering an intermediate to BeH by disproportionation to theinsoluble solid BeH and the soluble beryllium dihalide-Lewi's basecomplex. The solubility of the latter in many inert organic solventspermits its used in a cyclic process.

The process of this invention also provides a means for the purificationof beryllium hydride prepared by conventional methods. The crudeberyllium hydride is reacted with a beryllium chloride, berylliumbromide, or beryllium iodide in the presence of an inert solvent and aLewis base at a temperature within the range of about 0 to 100C. andpreferably within the range of about 25 to C. to form a solublehaloberyllium hydride in accordance with the following equation:

where X and Z are the same as defined for Equations 1 and 2. The ratioof the amount of beryllium halide to the amount of the beryllium.hydride should be at least 1: 1. Higher ratios of the halide acceleratesolubilization of the beryllium hydride, but tend to hinder itssubsequent recovery via disproportionation of the haloberyllium hydridein accordance with the process of Equation 2. A ratio of berylliumchloride to beryllium hydride of 1:1 is preferred. At least 2 moles, andpreferably 3 to 4 moles, of Lewis base are used per mole of berylliumhalide. For example, treatment of polymeric solid BeH with berylliumchloride and a Lewis base, e.g., diethyl ether, in a ratio of 1:1:4 insolution in an inert solvents, e.g. toluene at 70C. yields the solubleaddition compound Bel-l -Becl fi 2ClBel-l, i.e., chloroberylliumhydride. Solubilizing BeH in this manner provides a novel means ofpurification, allowing the isolation of high purity beryllium hydride bydisproportionation of the chloroberyllium hydride in accordance with thereaction and conditions of Equation 2.

In addition, novel haloberyllium hydride-Lewis base complexes have beenprepared. As discussed above, such complexes are useful in thepreparation of pure beryllium hydride, useful in powder metallurgy andin high energy propellant formulations. Moreover, chloroberylliumhydride is useful as a reducing agent. Also chloroberyllium hydride canbe reacted with olefins to form the corresponding mixed chloroberylliumalkyls which can then be disproportionated to beryllium alkyls andberyllium chloride, thus offering a novel route to beryllium alkylsother than by means of Grignard reagents. Further, beryllium alkyls areintermediates in the conventional preparation of beryllium hydride.

The following examples illustrate the preparation of a haloberylliumhydride-Lewis base complex and various ways of disproportionating such acomplex to obtain pure beryllium hydride. Example Vll illustrate vacuumdisproportionation; Example Vlll illustrates disproportionation inbenzene; Example 1X illustrates disproportionation in dimethyl sulfide;and Example X illustrate disproportionation by slow addition of thehaloberyllium hydride-Lewis base complex to an evacuated zone.

EXAMPLE 1 1.95 Grams of freshly distilled beryllium chloride dissolvedin m1. of dry dimethyl sulfide was placed in a 250 m. glass pressurebottle half-filled with stainless steel balls Vs inch in diameter. Tothis solution was added 0.61 g. of sodium hydride dispersed in 7.5 ml.of kerosene. The reaction mixture was ball-milled at ambienttemperatures for 16 hours. The reaction mixture was then filtered andthe clear filtrate analyzed. The filtrate contained 6.05 mmoles ofsoluble chloroberyllium hydride, ClBeH:2SMe corresponding to aconversion of 24.9% based on the initial charge of beryllium chloride.Analysis by flame spectroscopy disclosed absence of sodium in thefiltrate showing that all the sodium was retained in the solid phase andthat the soluble chloroberyllium hydride was free of sodium.

EXAMPLE II The procedure of Example I was repeated except that diethylether was used as the solvent instead of dimethyl sulfide. The reactionmixture consisted of 5.25 g. of beryllium chloride dissolved in 104.4 g.of diethyl ether and 1.71 g. of sodium hydride suspended in 6.8 g. oftoluene. The mixture was ball-milled at room temperature for 3 days andfiltered. Hydrolytic analysis of 29.13 g. sample of the clear filtrategave the soluble atomic ratios of l-lzBezCl of 1.00:1.02:1.03 incontrast to theoretical values of 1:111 for l-lBeCl. l-l'being an activehydrogen released as gaseous hydrogen on hydrolysis. Flame spectroscopydisclosed absence of sodium in the hydrolysate showing that the productwas sodium-free chloroberyllium hydride.

Another sample (49.0 g.) of the filtrate was pumped in high vacuum atroom temperature to remove the toluene and ether solvent. The residuewas redissolved in 50 ml. of dry diethyl ether and filtered. A 19.2 g.sample of this ether solution was pumped overnight at C. Thenon-volatile residue consisted of a colorless liquid whichupon analysisgave an atom-mole ratio of beryllium to ether of 1.00: 1 .95. in goodagreement with the theoretical value 1:2 for the dietherate, ClBeH:2O(CH A second sample (14.56 g.) of the ether solution was pumped at 0C. todistill off the excess ether. The liquid residue was then pumped in highvacuum mm. Hg) at room temperature for 4 hours. The non-volatile residuewas colorless liquid which exhibited an atom-mole ratio of beryllium toether of 1.00:0.96 in contrast'to the theoretical ratio 1:1 for themonoetherate, ClBeH:O(C H Continued pumping at 30C. for additional 12hours resulted in the loss of more ether, leaving a solid residue with aberyllium to ether ratio of 1.00 to 0.52.

A. When Example 11 was repeated, using trimethylamine instead of diethylether, the product was soluble chloroberyllium hydride-trimethylaminate.

B. When Example 11 is repeated using BeBr instead of BeCl solublebromoberyllium hydride-diethyl etherate is obtained.

C. When Example 11 is repeated using Bel instead of BeCl the product issoluble iodoberyllium hydridediethyl etherate.

EXAMPLE 111 The procedure of Example 1 was repeated except that a mixedsolvent was used consisting of 80% by volume of anisole, 15 percent ofdiethyl ether, and 5% of kerosene. Soluble chloroberyllium hydride wasobtained, demonstrating the use of alkyl-aryl ethers as solvents.

EXAMPLE IV The procedure of Example 11 was repeated except that lithiumhydride was reacted with beryllium chloride, giving an ether-solublechloroberyllium hydride.

EXAMPLE V A mixture consisting of 114.8 g. of beryllium chloride, 198.8g. of diethyl ether, 36.8 g. of sodium hydride and 735.2 g. of benzenewas heated in a stirred pressure reactor at 90C. for 11 hours. Thereaction mixture was cooled to room temperature and filtered. A 1.41 g.sample of the filtrate was analyzed. The soluble ratios of l-l:Be:Clwere 0.955:1.00:1.09 compared to the theory 1:1:1 for l-lBeCl.

EXAMPLE VI A mixture of 8.2 g. of beryllium chloride, 150 ml. of diethylether, 5.0 g. sodium hydride and 25 g. of kerosene was charged to a 300ml. pressure reactor. The reaction mixture was stirred and heated at130C. for 24 hours. After cooling to room temperature the mixture wasfiltered and the filtrate analyzed. The filtrate con tained a traceamount of beryllium chloride but no soluble hydride, indicating thatunder these reaction conditions essentially all the beryllium contentwas retained in the solid phase as Bel'l in admixture with byproductNaCl and residual Nal-l. Isolation of beryllium hydride from the solidphase was not possible because BeH NaCl and NaH are all insoluble indiethyl ether.

EXAMPLE Vll A mixture containing 41% ClBeHzOEt and 59% BeCl :OEt waspumped in high vacuum at 63C. for 2 days. The non-volatile residue wasthoroughly mixed with benzene and'the resulting suspension transferredto a Soxhlet extractor equipped with a fritted disc and withsyrum-capped side arms. The mixture was filtered and the solublechloride was extracted with dimethyl sulfide for three days. A sample ofthe insoluble solid suspended in dimethyl sulfide was transferred via asyringe to a tared 50 ml. round bottom flask provided with a 2mm. Teflonneedle valve (Fisher-Porter Model No. 795-005 a Teflon coated magneticstirrer. and an O-ring ball joint. The flask was attached to the vacuumline through the ball joint and the solvents were removed by pumping inhigh vacuum at room temperature and finally by heating at 101C.overnight. The flask was cooled to room temperature, filled withnitrogen, weighed and the contents hydrolyzed with dilute acetic acid inthe presence of toluene. The hydrogen evolved was passed through 3U-tubes cooled at 196C., collected in a calibrated volume by means of aToepler pump and measured. The hydrolysate and the l96C. condensate werecombined and analyzed for beryllium, chloride and ether. The productcontained 81.5 wt. Bel-l with 1.2 wt. (C H O and 5.8 wt. C1(l-l/Cl ratio90/ 1 EXAMPLE Vlll A mixture of 139.2 mmoles ClBel-lzOEt and 19.0

' mmoles BeCl OEt was dissolved in 171 g. benzene.

The solution was vacuum-distilled at 65C with total take-off, utilizingbenzene vapor as a carrier for the evolved ether. Fresh benzene solventwas added periodically to maintain the by-product BeCl zOEt in solution.The distillation was continued for 5 hours, collecting the distillate ina receiver cooled by dry ice-acetone. The reaction mixture was filteredand the insoluble Bel-l residue was subjected to Soxhlet extraction withdimethyl sulfide for 23 hours. A sample of the solid suspension waswithdrawn, and vacuum-dried at C. for 15 hours. Analysis showed aproduct purity of 69% Bel-l with 8.2 wt. C1 (l-ll/Cl ratio of 54/1) and1 1.0 wt. Et O. A second sample was withdrawn and vacuum-dried at 97C.It gave a purity of 77 wt. Bel-l with 3.6 wt. B 0 and 7.8 wt. Cl (H/Clratio 63/1).

EXAMPLE [X A sample of 129.5 mmoles of ClBeH-etherate in admixture withBeCl :OEt with observed ratios of H:Be:Cl'.Et O of 1.011.221.3112 wasadded to 130 ml. dimethyl sulfide at room temperature. The resultingsolid was filtered and extracted with benzene for 2 days. The insolubleresidue, suspended in benzene, was transferred to a tared hydrolysisflask and the solvent distilled under vacuum at room temperature. Thesolid residue was heated at 108 with pumping in high vacuum for 16hours. Hydrolytic analysis showed the product to be 90 wt. BeH

EXAMPLE X A sample consisting of 316 mmoles ClBeH: OEt 58.2 mmoles BeCl:OEt and 94.2 mmoles of Et O was dissolved in 68 grams of benzene. Thesolution was added incremetally (1-5 ml.) to an evacuated flask heatedat 6570C. After each addition the mixture was stirred for 1-2 minutes ina closed system and then rapidly evacuated to remove ether and benzene.The intermittant addition was continued for 6.0 hours after which thereaction mixture was vacuum heated at 55C. for an additional 8 hours.The ether and benzene were condensed in two traps cooled at 80 and l96C.The amount of ether evolved was found to be 256 mmoles in good agreementwith 252.2 mmoles expected from summation of 158 mmoles resulting fromdisproportionation of (316 mmoles) ClBeH:OEt plus 94.2 mmoles present inthe initial sample as excess Et O.

The solid reaction mixture was then thoroughly mixed with 125 ml.benzene to solubilize the BeCl :O- Et and residual ClBeHzOEt and theresulting suspension was filtered. The filtrate contained 87.7 mmoles ofClBeH:OEt This corresponded to 72% disproportionation.

Repetition of this experiment starting with more dilute solution ofClBeH2OEt (0.6 molar) in benzene re- 8 sulted in 87% conversion based onconsumption of soluble hydride.

Residual soluble chloride was extracted with dimethyl sulfide. Thedimethyl sulfide extract contained no soluble hydride. A sample of theinsoluble solid was vacuum heated at 135C. for 15 hours and gave apurity of 74.1 wt. BeH with 10.7 wt. Cl and 5.0 wt. Et O.

There are disclosed above a number of embodiments of the inventionherein presented, however, it is possible to produce still otherembodiments without departing from the inventive concept hereindisclosed. It is desired, therefore, that only such limitations beimposed on the appended claims as are stated therein.

What is claimed is:

l. A process for the production of beryllium hydride which comprisesdisproportionatng a haloberyllium hydride-Lewis base complex having theformula:

wherein X is a halogen selected from the group consisting of chlorine,bromine and iodine, Z is a Lewis base which does not contain a protonichydrogen and n is 0.5 to 2, and recovering solid beryllium hydride.

2. 'lhe process of claim 1 wherein Z is selected from the groupconsisting of dialkyl ethers, diaryl ethers, alkyl aryl ethers, dialkylsulfide and tertiary amines.

3. The process of claim 1 wherein Z is diethyl ether, dimethyl sulfideor trimethyl amine.

4. The process of claim 1 wherein Xis chlorine.

5. The process of claim 1 wherein X is bromine.

6. The process of claim 1 wherein said disproportionation is effected byheating said haloberyllium hydride- Lewis base complex at a temperaturebelow about C under vacuum thereby distilling off Lewis base.

7. The process of claim 1 wherein said disproportionation is effected byheating said haloberyllium hydride Lewis base complex at a temperatureabove about l00C. thereby removing the Lewis base.

1. A PROCESS FOR THE PRODUCTION OF BERYLLIUM HYDRIDE WHICH COMPRISESDISPROPORTIONATING A HALOBERYLLIUM HYDRIDE-LEWIS BASE COMPLEX HAVING THEFORMULA:
 2. The process of claim 1 wherein Z is selected from the groupconsisting of dialkyl ethers, diaryl ethers, alkyl aryl ethers, dialkylsulfide and tertiary amines.
 3. The process of claim 1 wherein Z isdiethyl ether, dimethyl sulfide or trimethyl amine.
 4. The process ofclaim 1 wherein X is chlorine.
 5. The process of claim 1 wherein X isbromine.
 6. The process of claim 1 wherein said disproportionation iseffected by heating said haloberyllium hydride-Lewis base complex at atemperature below about 100*C under vacuum thereby distilling off Lewisbase.
 7. The process of claim 1 wherein said disproportionation iseffected by heating said haloberyllium hydride-Lewis base complex at atemperature above about 100*C. thereby removing the Lewis base.